The Institute of Medicine report stops short of asking the federal government to retire all the animals, saying future unseen threats to human health may require their use.

Two chimpanzees, former members of a colony used for biomedical research,… (Eric Hasert, Stuart News )

Chimpanzees remain indispensable for biomedical and behavioral research that benefits humans, but only in a small number of circumstances and likely not for long, according to a new report from the Institute of Medicine.

After nine months of deliberation, a panel of independent experts judged that most current experiments involving man's closest primate relative can safely be discontinued. But the experts stopped short of calling on the federal government to retire all of about 600 chimps in its care, cautioning that unseen threats to human health "may require the future use of the chimpanzee."

The director of the National Institutes of Health, Dr. Francis Collins, said he accepted the panel's recommendations and promised to name a working group to figure out how to implement them.

In a news conference Thursday, Collins predicted that about half of the 37 NIH-sponsored studies that use chimpanzees would be phased out. The working group will consider how many chimpanzees the federal research agency should keep in captivity for possible use and how many can be retired to sanctuaries scattered across the country, he said.

The NIH asked the Institute of Medicine for advice on using chimps in biomedical experiments last December after the agency ordered a group of retired animals housed at a government holding facility in Alamagordo, N.M., moved to an active research site in Texas. The proposal drew howls of protest from animal rights activists, primatologists and a small group of lawmakers who have tried and failed repeatedly to pass legislation banning the use of chimps in biomedical research.

The United States and the African nation of Gabon are the only countries that still permit active experimentation using chimpanzees, a species that exhibits clear signs of love, complex social organization, self-awareness and distress.

Research published in June found plentiful evidence of distress, especially, in 168 chimpanzees previously used in biomedical research. Comparing the retired biomedical subjects to a wild population of chimps, the study in the scientific journal PLoS One found signs of depression in 58% of the biomedical retirees and signs of post-traumatic stress disorder in 44% — afflictions virtually absent in wild populations.

"Chimps are clearly emotionally sensitive and intelligent beings," said Dr. Hope Ferdowsian, the lead author of that study and a former director of research policy with the Physicians Committee for Responsible Medicine, which lobbies against using the animals for research. Chimps ply wide ranges and live in large social groups with tight bonds between mother and child and among friends, Ferdowsian said. "Their needs clearly cannot be met in a lab setting."

Animal rights advocates and lawmakers who support the Great Ape Protection and Cost Savings Act praised the Institute of Medicine report. Wayne Pacelle, president of the Humane Society of the United States, said he was "tremendously encouraged" by the findings, which he said "lead to only one reasonable conclusion: It's time to end the use of chimps in harmful, invasive research."

In a statement released Thursday, People for the Ethical Treatment of Animals said the NIH's internal review should culminate in "a complete ban on experiments on chimpanzees in laboratories."

Collins' embrace of the Institute of Medicine recommendations likely marks a new chapter in biomedical research. Captive chimpanzees have yielded key advances in therapies for human diseases, including cancer, hepatitis and autoimmune diseases such as rheumatoid arthritis.

But powerful computers, new lab techniques and genetic engineering have steadily reduced the need to use chimpanzees as human stand-ins. Meanwhile, progress in understanding other diseases, such as HIV/AIDS, has underscored that while chimps and humans share much DNA, not all diseases behave the same in Pan troglodytes as they do in Homo sapiens.

"We believe the chimp has been a valuable animal model in the past," said Jeffrey P. Kahn, a Johns Hopkins University bioethicist who was chairman of the Institute of Medicine panel. But, he said, "there clearly is a trajectory indicating a decreasing need for chimpanzee studies.… We see this as an area of even further diminishing necessity."

After evaluating the state of research on vaccines, viral pathogens and targeted biologic therapies, the panel concluded that efforts to test the safety of targeted immune-boosting medicines — so-called monoclonal antibodies — still rely on chimpanzee research subjects to test safety and effectiveness.

That reliance is quickly being eroded by the genetic alteration of mice, rats and other animals to mimic the human immune system, as well as by techniques that gauge humans' response to tiny doses of these biologic medicines. But until those alternatives means of testing are widely available, the committee said, the NIH will likely need to support limited use of chimps in such trials.